is_callable

(PHP 4 >= 4.0.6, PHP 5)

is_callable --  Verify that the contents of a variable can be called as a function

Description

bool is_callable ( mixed var [, bool syntax_only [, string &callable_name]] )

Verify that the contents of a variable can be called as a function. This can check that a simple variable contains the name of a valid function, or that an array contains a properly encoded object and function name.

The var parameter can be either the name of a function stored in a string variable, or an object and the name of a method within the object, like this:

array($SomeObject, 'MethodName')

If the syntax_only argument is TRUE the function only verifies that var might be a function or method. It will only reject simple variables that are not strings, or an array that does not have a valid structure to be used as a callback. The valid ones are supposed to have only 2 entries, the first of which is an object or a string, and the second a string.

The callable_name argument receives the "callable name". In the example below it's "someClass:someMethod". Note, however, that despite the implication that someClass::SomeMethod() is a callable static method, this is not the case.

<?php
//  How to check a variable to see if it can be called
//  as a function.

//
//  Simple variable containing a function
//

function someFunction()
{
}

$functionVariable = 'someFunction';

var_dump(is_callable($functionVariable, false, $callable_name));  // bool(true)

echo $callable_name, "\n";  // someFunction

//
//  Array containing a method
//

class someClass {

  function
someMethod()
  {
  }

}

$anObject = new someClass();

$methodVariable = array($anObject, 'someMethod');

var_dump(is_callable($methodVariable, true, $callable_name));  //  bool(true)

echo $callable_name, "\n";  //  someClass:someMethod

?>

See also function_exists() and method_exists().